1. Field of the Invention
This invention relates to fluid pressure regulators used with mechanical or other devices requiring a regulated constant flow of fluid pressure for powering operation of the device. More particularly it relates to an in line pressure regulator for tools which both regulates the pressure received by the tool from a conventional fluid pressure source during operation, and, passively relieves leftover pressure inside the tool and regulator when the pressure regulator is disconnected from the pressure source or when the pressure source is turned and vented.
2. Prior Art
Pressure regulators are commonly used in the United States and throughout the world to regulate the pressure received by pneumatic and hydraulic tools for compressors or other pressure sources. Most such tools have an optimum range of operation for the pressurized fluid stream which provides them energy to operate. However, most compressors and other conventionally used pressurized fluid stream sources operate at fluid pressures above the optimum range required by the tool connected to them.
Common power tools such as pneumatic air hammers which drive nails into wood on construction sites, pneumatic staplers, and pneumatic and hydraulic saws used in construction, butcher shops, and even dentist offices, require a constant regulated fluid stream to operate effectively. Currently such a regulated pressurized fluid stream is maintained by a fluid pressure regulator located between the conventional pressurized fluid source and the connected tool.
There exists a common hazard with all such devices when connected to a source of compressed fluid. When the conventional source of the pressurized fluid is disconnected from the inlet side of a conventional pressure regulator, pressurized fluid remains in the tool and on the regulated exit side of the regulator. The disconnection from the fluid source thus provides a false sense of security to the user because the tool, having a pressurized fluid source still available in the regulator and the tool itself, is still capable of operation for another cycle if the tool trigger is activated.
Many a carpenter has been seriously injured by an "unloaded" nail gun thinking that the tool would not operate after it was disconnected from a compressor line. Severe injury has also been caused by the operation of rotary saws and drills which will also operate for a short time on the reservoir of pressurized fluid that exists between the outlet of current regulators and the tool itself.
There are a number of approaches advanced in prior art which address either the safety disconnect issue or the pressure regulating requirements. However, prior art fails to address both requirements leaving a constant hazard to users of such devices.
U.S. Pat. No. 4,253,683, Jentsch et al., teaches a safety bleed stop hose coupling for pneumatic tools. Jentsch notes the extreme hazard to tool users who disconnect the tool from a pressurized line feeding the tool. If the line is disconnected while under pressure the line can seriously injure the user. Jentsch solves this problem with a telltale hiss sound alerting the user to the pressure still contained in the line. The user therein can activate a bleed valve to release the pressure and then disconnect the tool. However, Jentsch offers no pressure regulation means and requires an affirmative action by the user to release the pent up pressure in the line which is easily forgotten on a busy job site.
U.S. Pat. No. 3,524,465, Sadler, teaches an in line pressure regulation device wherein pressure received on the inlet side is transferred to the outlet side and excess pressure beyond a predetermined point is relieved through a bleed valve. However, Sadler in operation would still allow pressure at the predetermined amount to stay in the tool used and the outlet side of the regulator upon release of pressure feeding the inlet. Thus, while the tool received pressurized fluid at a predetermined amount, that pressure is not released upon disconnecting from the source and poses an extreme hazard to tool users who unaware that the tool will still operate.
Pressure regulation is also taught in U.S. Pat. No. 5,222,518 Fisher et al. Fisher however addresses only the problem of excess pressure in lines caused by excess pressure from the source or a blockage of a return line in a hydraulic system. Fisher does not allow for the release of line pressure upon disconnecting from a pressure source and is not intended to be a constant pressure regulation device.
Safety in the control of a power tool is addressed in U.S. Pat. No. 3,970,110 Schaedler et al. Schaedler teaches a safety switch at the trigger of a power tool which must be concurrently activated with a separate trigger switch to allow operation of the tool. However, Schaedler does not allow for constant fluid pressure regulation or passive release of pressure upon disconnecting from the pressure source. Thus the tool may operate if the user concurrently activates the safety and the trigger using pressure stored in the tool even if disconnected from a power source.
Another method of addressing the safety concerns in power tools is advanced by U.S. Pat. No. 4,794,273 McCullough et al. MuCullough teaches and electronic sensing means which monitors the users grasping of the tool and power supply line. If the user grasps both the tool and the supply line, the electronic sensing means will allow the tool to operate upon activation of the trigger by the user. However if the supply line is not held at the same time as the tool, the electronic sensing means will not allow the tool to operate. Once both the tool and the supply line are released by the operator, the electronic sensing means de-energizes the tool. MuCullough however requires the use of a complicated electronic sensing means which would not fare well in the rough use of construction workers and it provides no pressure regulation means.
There thus exists the need for an in line fluid pressure regulating device providing fluid at a relatively constant predetermined pressure which also provides the safety of passive release of the pressurized fluid left in the regulation device and in the connected tool operated by the pressurized fluid.